During wireline operations for conducting downhole activities in deep wells such as wells for producing petroleum products, it is a standard safety procedure to mount a wireline blowout preventer at the bottom of the pressure control system of a wireline tool that is connected to the wellhead system. The wireline blowout preventer allows pressure to be contained within the well with the wireline in place, by closing one or more pairs of rams around the wireline. Above the blowout preventer wireline equipment typically employs upper and lower lubricators that are interconnected by means of a union and a stuffing box that maintains a pressure containing seal about the wireline as it is moved into or from the wireline equipment. The upper portion of the wireline tool is typically provided with a wireline pulley that directs the running portion of the wireline downwardly to the winch of wireline handling apparatus located at or about the level of the ground or working floor about the wellhead. A downhole tool string is connected to the wireline and is typically capable of descending through the well tubing by gravity or by pressure induced force such that it moves downwardly within the well to the level of working operations. After working operations have been completed, the tool string is withdrawn upwardly through the well tubing by force applied to the wireline by the wireline winch. In some cases, the tool string is propelled upwardly through the tubing string by means of pressure induced force so that the wireline is used only for purposes of control and for insuring positioning of the tool string at the appropriate level within the well.
As the wireline tool string reaches the upper limits of its travel it traverses the vertical flow passage of the wellhead. Occasionally a tool string is moved upwardly sufficiently fast that it impacts against internal structure of the wellhead or wireline equipment and under such circumstances, the tool string can become stuck in a position preventing closure of the wireline blowout preventer and also preventing closure of the wellhead safety valves such as the top and bottom master valves. When this occurs, it is impossible to return the wellhead system to a safe condition unless the wireline tool string can be moved downwardly or upwardly to a position clearing at least one of the safety valves of the wellhead or blowout preventer. Different jarring mechanisms are typically employed in this case to release the tool string from its stuck position; however, if the jars fail to release the wireline tool from its stuck position it may be impossible to safely shut-in the well without necessitating killing it. Obviously it is quite expensive to kill a well simply to assure safe removal of a stuck wireline tool string. This can cause severe damage to the well and can be detrimental to the production of the well once it is restored to producing condition. It is desirable, therefore, to provide an efficient mechanism for rendering wireline equipment to a safe condition to thus enable a stuck wireline tool string to be safely released from a stuck condition and so that the well may be efficiently shut-in for completion of wireline service activities.
It is a principal feature of the present invention to provide a novel mechanism for wireline equipment which is capable of severing the wireline of a stuck wireline tool string to thereby release the connection between the wireline and the wireline tool string.
It is also a feature of the present invention to provide a novel mechanism for automatically developing an internal safety seal within the wireline equipment when the wireline is severed such that additional wireline equipment may be assembled in end-to-end relation to the wireline equipment initially in use and which is provided with another wireline tool that is capable of accomplishing release and handling of a stuck wireline tool string.
It is an even further feature of the present invention to provide wireline equipment having the capability of severing the wireline and developing an internal safety seal and also being capable of being rendered to a completely open condition to thus provide for passage of another wireline tool string through the housing of the wireline equipment for achieving service and handling operations with respect to a stuck wireline tool string.